Numerical investigations of liquid–solid slurry flows in a fully developed turbulent flow region (original) (raw)
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A numerical study of developing slurry flow in the entrance region of a horizontal pipe
Computers & Fluids, 2008
In this paper, a simplified 3-D algebraic slip mixture (ASM) model was introduced to obtain the numerical solution in sand-water slurry flow. In order for the study to obtain the precise numerical solution in fully developed turbulent flow, the RNG K-e turbulent model was used with the algebraic slip mixture model. An unstructured (block-structured), non-uniform grid was chosen to discretize the entire computation domain, and a control volume finite difference method (CVFDM) was applied to solve the governing equations. The mean pressure gradients from the numerical solution in the fully developed turbulent flow were compared with the authors' experimental data and that in the open literature to validate the simulation results. The solutions were found to be in good agreement with the experimental data. The numerical investigations have focused mainly on illustrating and comparing the developing processes of volume fraction and density distributions, mean velocity profiles, and mean skin friction coefficient distributions in the entrance region. It was found that the difference of friction factors between single-and double-species slurries increases along flow direction in most part of the entrance region.
Validation of friction factor predictions in vertical slurry flows with coarse particles
Journal of Hydrology and Hydromechanics, 2020
The paper presents validation of a mathematical model describing the friction factor by comparing the predicted and measured results in a broad range of solid concentrations and mean particle diameters. Three different types of solids, surrounded by water as a carrier liquid, namely Canasphere, PVC, and Sand were used with solids density from 1045 to 2650 kg/m3, and in the range of solid concentrations by volume from 0.10 to 0.45. All solid particles were narrowly sized with mean particle diameters between 1.5 and 3.4 mm. It is presented that the model predicts the friction factor fairly well. The paper demonstrates that solid particle diameter plays a crucial role for the friction factor in a vertical slurry flow with coarse solid particles. The mathematical model is discussed in reference to damping of turbulence in such flows. As the friction factor is below the friction for water it is concluded that it is possible that the effect of damping of turbulence is included in the KB f...
Mathematical modelling of slurry flow with medium solid particles
The paper deals with a solid-liquid turbulent flow with moderate and high solids concentration, which appears widely in chemical and mining industries. The slurry transported through a straight pipe contains medium solid particles of averaged diameters higher than 0.1 mm and lower than 0.8 mm surrounded by water as a carrier liquid. Mathematical model assumed that that flow is turbulent, fully developed and axially symmetrical with steady viscosity equal to carrier liquid viscosity and density depending on solids concentration. The model uses time averaged momentum equation and the problem of closure is solved by two-equation turbulence model, which includes a new turbulence damping function specially developed for such slurry flows. The mathematical model is suitable to predict slurry flow with medium solid particles and solids concentration from 10% to 40% by volume. Numerical predictions were compared with measurements showing good accuracy. Possible reason of turbulence damping ...
This present study represents a numerical analysis of sand water slurry flow considering different sand particle sizes through horizontal pipeline of 5.5m length and 103 mm diameter at high velocity. Computational fluid dynamics was used for the numerical simulation; Eulerial two phase model was selected for modeling the multiphase flow and RNG K-epsilon model was adopted for modeling the turbulent flow. 90µm, 150µm and 270µm sand particle (Sp. Gravity 2.65) sizes were considered for this present study for a mixture flow velocity of 5.4m/s at various solid volumetric concentration levels (20%, 30% and 40%). The behaviour of various flow parameters viz. concentration distributions, velocity distributions and pressure drop were analyzed from the numerically simulated results. The influence of particle size and solid volumetric concentrations on various flow parameters were analyzed in this study. Finally the simulated results of pressure drop were validated with the experimental data available in previous literature. I. INTRODUCTION Demands for conveyance of solid materials through pipelines over a long distance have increased dramatically over the last few decades. This is because this mode of transportation of solid materials is more economical, more environment friendly, causes less air pollution and less road traffics than the conventional mode of solid material transportations. Many industries like power generation industries, pharmaceutical, construction industries, city municipality, oil and gas industries food processing industries etc handle the solid material transportation through pipelines. Generally solid materials are mixed with fluid and slurry is formed, then the slurry is made to flow through the pipeline for transportation. The flow patterns of these slurry (Solid-fluid mixture) shows a remarkable difference with the flow patterns of pure fluid flow through the pipeline and hence to obtain a detailed information about the slurry flow process behaviour of different flow parameters need to be observed carefully. Slurry flow is a multiphase complex flow problem. Computational fluid dynamics (CFD) is a numerical analysis platform where a wide range of multiphase flow problems can be analyzed with greater ease and low cost which would have been almost impossible with experimental work. CFD allows the researchers to adopt different complex multiphase models for proper modeling of the slurry flow.
Numerical investigation of solid-liquid slurry flow through an upward-facing step
Journal of Hydrology and Hydromechanics, 2013
The flow of a solid-water mixture through an upward-facing step in a channel is numerically investigated. The effect of expansion ratio, mean solids volume fraction and particle diameter on the velocity field, pressure distribution and solid volume fraction field is studied. Expansion ratios of 0.50 and 0.67, particle diameter of 125 µm and 440 µm and mean solid volume fraction between 0.05 and 0.20 are considered. Particle density is 2465 kg m-3. An Eulerian twofluid model is used to simulate the flow. Due to the lack of experimental data, the model was validated by comparison to other numerical investigations and to experimental data about the horizontal pipe case. Afterwards, it is studied the effect of the above mentioned parameters upon the degree of coupling between the phases and the extension of the disturbance region in the pressure and solid volume fraction fields downstream the step. Parameters of engineering interest, such as the reattachment length and the pressure recovery downstream the enlargement, are investigated.
It has been well demonstrated in the literature that slurries comprising a viscous carrier fluid plus coarse solids fraction segregate under laminar pipe flow conditions. Velocity and concentration distributions in the pipeline are non-symmetrical, with the coarse solids concentrated in a lower layer, with a particle-lean upper layer above. Laminar flow friction pressure gradient versus velocity plots for these flow conditions follow the general appearance of homogeneous laminar flow. However, the segregated, non-symmetrical flow has a significant effect on the friction pressure gradient. In this paper the authors evaluate the performance of a two-layer laminar flow model against measured laminar flow pressure gradient data for kaolin plus sand slurries published by Kabengele et al (2012). The model is based primarily on the work of Pullum et al (2004) as previously described by Fraser & Goosen (2019) and incorporating the concept of a "gelled bed" condition as described by Talmon et al (2004).
Computational fluid dynamics modelling and experimental study of erosion in slurry jet flows
International Journal of Computational Fluid Dynamics, 2009
The application of computational fluid dynamics (CFDs) in the area of porous media and adsorption cooling system is becoming more practical due to the significant improvement in computer power. The results from previous studies have shown that CFD can be useful tool for predicting the water vapour flow pattern, temperature, heat transfer and flow velocity and adsorption rate. This paper investigates the effect of silica gel granular size on the water adsorption rate using computational fluid dynamics and gravimetric experimental (TGA) method.
Computational modeling of free-surface slurry flow problems using particle simulation method
Journal of Central South University, 2013
The particle simulation method is used to solve free-surface slurry flow problems that may be encountered in several scientific and engineering fields. The main idea behind the use of the particle simulation method is to treat granular or other materials as an assembly of many particles. Compared with the continuum-mechanics-based numerical methods such as the finite element and finite volume methods, the movement of each particle is accurately described in the particle simulation method so that the free surface of a slurry flow problem can be automatically obtained. The major advantage of using the particle simulation method is that only a simple numerical algorithm is needed to solve the governing equation of a particle simulation system. For the purpose of illustrating how to use the particle simulation method to solve free-surface flow problems, three examples involving slurry flow on three different types of river beds have been considered. The related particle simulation results obtained from these three examples have demonstrated that: 1) The particle simulation method is a promising and useful method for solving free-surface flow problems encountered in both the scientific and engineering fields; 2) The shape and irregular roughness of a river bed can have a significant effect on the free surface morphologies of slurry flow when it passes through the river bed.
Improvements in the numerical prediction of fully-suspended slurry flow in horizontal pipes
Powder Technology, 2015
A new two-fluid model is presented for the simulation of fully-suspended liquid-solid slurry flows in horizontal pipes. The model is a significant upgrade of an earlier one [G.V. Messa, M. Malin, S. Malavasi, Powder Technol. 256 (2014), 61-70], and the main improvements concern the use of: (1) a new wall boundary condition for the solid phase (2) a more general correlation for the viscosity of the mixture, which allows accounting for particle shape; (3) a different solution algorithm, which reduces significantly the already low computational burden. By comparison with experimental data available in the literature regarding sand-water slurries, the model showed wider applicability compared to the earlier one. In particular, the validation was carried out for the following flow conditions: pipe diameter between 50 and 200 mm; particle size between 90 and 640 μm; mean delivered solid concentration up to 40% by volume; and slurry superficial velocity up to 9 m/s. Slurries in which the dispersed phase consists of spherical glass beads have been briefly explored too. The improvements considerably increase the accuracy of the pressure gradient predictions, without affecting the model's capability in reproducing the other features of these flows of most engineering interest, namely solid volume fraction distribution and velocity distribution.
Computational Fluid Dynamics Simulation of the Solid- Liquid Slurry Flow in a Pipeline
2013
An attempt has been made to develop a generalized slurry flow model using the computational fluid dynamics simulation technique (CFD) to have better insight about the complexity of slurry flow in pipelines. The model is utilized to predict concentration profile, velocity profile and their effect on pressure drop taking the effect of particle size into consideration. At first a two-dimensional model has been developed to understand the influence of the particle drag coefficient with the different conditions. Then, three-dimensional model has been generated to complete understanding and visualization of slurry flow behavior. The two-fluid model based on the Eulerian-Eulerian approach along with a standard k-e turbulence model with mixture properties was used, whereby both the liquid and solid phases are considered as continua. The Eulerian model is the most complex and computationally intensive among the multiphase models. It solves a set of momentum and continuity equations for each ...